Functional dyspepsia (FD) is a common clinical condition with major symptoms including postprandial fullness, early satiety, and pain or burning sensation in the upper abdomen [1]. Current studies suggest that the pathogenesis of FD may be related to duodenal inflammation and increased eosinophil infiltration [2]. Interestingly, dysbiosis of the intestinal microbiota is also a significant factor in the development of functional dyspepsia [3].

Simo Decoction is a traditional Chinese medicine composed of Fructus aurantii, Radix aucklandiae, Semen arecae as well as Radix linderae [4]. The Simo Decoction has been recognized as a highly effective and safe treatment regimen for patients diagnosed with FD [5]. Simo Decoction could alleviate the gastrointestinal side effects of chemotherapy via alteration of gut microbiota [6]. Golden Bifid might improve gastrointestinal (GI) symptoms in patients with diarrhea-predominant irritable bowel syndrome through microbiota modulation [7]. The Golden Bifid strain can act as a lactulose substitute in the prevention of minimal hepatic encephalopathy by modulating the Bifidobacterium rati [8]. Therefore, we speculated that the combination of Simo Decoction and Golden Bifid might produce better efficacy on FD.

Bifidobacterium lactis DN-173 010 was found to significantly enhance overall well-being and reduce the frequency of flatulence, although it did not effectively regulate bloating[9]. Bacteroides was found to be preponderant in the mucosal related duodenal microbiota at the phylum level [10]. Decreased relative abundance of Bacteroides was observed in animal models with FD complicated with liver depression-spleen deficiency syndrome [11]. Short chain fatty acids (SCFAs) are metabolized by intestinal microbiota from indigestible fiber-rich diets [12]. SCFAs, as crucial regulators in maintaining intestinal homeostasis, can elucidate the underlying mechanisms by which alterations in the composition of intestinal microbiota contribute to the pathophysiology of various human diseases [13]. Strikingly, SCFAs could diminish the abundance of pathogenic bacteria and increase beneficial intestinal metabolites to combat FD [14].

Considering the aforementioned reports, we thus proposed a possible mechanism of combination of Simo Decoction and Golden Bifid in treating FD, involved with regulation of intestinal microbiota and SCFAs. Therefore, a mouse model of food stagnation was constructed to simulate FD in humans, for the purpose of validating the hypothesis.